The present invention relates to an electrical connector. More particularly this invention concerns a method of injection-molding an electrical-connector shell.
An electrical connector of the type mounted on the end of a multiconductor cable typically has a dielectric shell holding a plurality of metal conductors and having a wall extending parallel thereto in an insertion direction. The shell is adapted to fit complementarily by joining together in the insertion direction with a fitting having other conductors that mate with those of the shell to form an electrical connection. Such connectors can be used to transmit signals or power and are typically intended for use under harsh conditions. Thus it is standard to provide some sort of seal between the shell and the fitting it mates with. When such a connector having a shell with a seal engages the appropriate fitting, moisture or the like cannot get into the actual conductors.
In a standard system the shell has a pair of annular concentric walls and the conductors are contained within the inner wall. The fitting engageable with it has an annular outer wall that fits between the inner and outer walls of the shell and central conductors that extend down in the inner wall of the shell and engage complementarily with the conductors therein. The seal can be provided at any of several interfaces.
European patent application 0,008,603 of Schauer describes such a conductor where a simple O-ring is provided in a groove on an outside of the shell holding two male conductors. Thus here the shell is a simple solid body and the seal is provided as a separate element which is fitted to the shell after it is manufactured, for instance by injection molding. German published application 197 19 436 of Siedentopf shows that the conductors can be molded right into the body of the connector.
In an unrelated field, U.S. Pat. No. 4,3743,422 of Kalriis-Nielsen proposes a pipe-joint seal comprising a stiff outer ring adapted to engage over the end and outer surface of an end of a piece of pipe, and a softer inner seal ring that engages over the end surface and projects down inside the pipe. In this manner, when an end of another pipe is fitted inside the piece provided with this seal, the inner ring will snugly engage the other pipe and form a tight seal. This two-part seal is formed in successive stages by molding in a very complex manner. The hard outer ring is made between two mold parts, one of which is reused for molding the inner ring. The inner ring is weakly attached to the outer ring, an insignificant problem as this system is not intended to withstand significant stresses parallel to the axial insertion direction.
It is therefore an object of the present invention to provide an improved electrical-conductor shell.
Another object is the provision of an improved method of making an electrical-conductor shell which overcomes the above-given disadvantages, that is which produces a shell suitable for use as an electrical conductor in a simple procedure with simple equipment.
A further object is to provide such a production method which produces a connector shell where a seal ring formed normally of an elastomer much softer than the plastic of the shell is very solidly anchored in the shell for resistance to axial forces.
An electrical-connector shell is made according to the invention by first casting of a first plastic in a first mold a body having an inner wall extending parallel to an axis and having a radially outwardly directed surface, an outer wall extending parallel to the axis and having a radially inwardly directed surface confronting the radially outwardly directed surface and forming therewith an axially extending annular space, and an end wall closing an end of the space, joining ends of the inner and outer walls, and formed with an axially throughgoing hole opening adjacent one of the surfaces. Then this body cast in the first mold is enclosed in a second mold formed with an annular cavity open radially toward the one surface and extending to the hole. A second plastic is then injected through the hole into the cavity to form on the one surface an annular seal ring.
As a result of the in-situ formation of the seal ring and the fact that it extends down the one surface to and into the hole, this seal ring is very solidly anchored to the shell. The seal can in fact form an annular skirt extending all the way down the one surface to the end wall to maximize surface contact and ensure that it will remain solidly attached to the one surface.
According to the invention the one surface is the outer surface of the inner wall. Thus the seal projects outward and is formed in accordance with the invention with at least one radially projecting annular ridge, normally two to four.
The first plastic according to the invention is a polyamide, polybutylenterephthalate, or polyethylene terephthalate. Thus the shell body is quite hard and durable even up to temperatures as high as 40xc2x0 C. The second plastic is a silicone elastomer including a bonding agent or a thermoplastic elastomer so that it is fairly soft. This agent could be epoxy silane. When no agent is used, the one surface needs to be prepared, for instance by flaming. The thermoplastic elastomer can be polyetherblockamide with polycarbonate.
The electrical-connector shell has according to the invention a body formed unitarily of a first plastic with an annular inner wall extending parallel to an axis and having a radially outwardly directed outer surface, an annular outer wall extending parallel to the axis and having a radially inwardly directed inner surface confronting the outer surface and forming therewith an axially extending space, and an end wall closing an end of the space, joining ends of the inner and outer walls, and formed with an axially throughgoing hole opening adjacent one of the surfaces. It also has a seal ring of annular shape projecting radially from the one surface and having a portion extending along the one surface to and into the hole.